The overall objectives of the project are to identify and characterize carcinofetal antigens and proteins of the gastrointestinal tract. Work this coming year will be devoted to further studies of the antigenic determinants of Carcino-Embryonic Antigen by haptene inhibition, and characterization of an unusual molecular form of serum carcino-embryonic antigen. We intend to test a number of other synthetic glycopeptides of known chemical structure by haptene inhibition radioimmunoassay for CEA. We also intend to test the ability of several additional antisera to CEA for their ability to recognize the unique CEA antigenic determinant described above. We hope to further characterize this unique serum CEA-like material initially by sephadex gel filtration, perchloric acid solubility and isoelectric point. If enough sera containing the CEA-like antigen can be obtained, we hope to perform further purification and chemical analysis of this CEA-like antigen. BIBLIOGRAPHIC REFERENCES: Vrba, R., Alpert, E. and Isselbacher, K.J. Immunological heterogeneity of serum carcinoembryonic antigen (CEA). Immunochemistry 13:87089, 1976. Alpert, E. Human alpha-1-fetoprotein (AFP): Developmental biology and clinical significance, in Progress in Liver Diseases. H. Popper and F. Schaffner, eds. New York, Grune & Stratton, 1976, pp. 337-349.